The present invention relates generally to drill bits used in the oil and gas industry. More particularly, the invention relates to drill bits having diamond cutting surfaces.
Drill bits presently known to the industry which utilize either natural or synthetic diamonds as the cutting elements in the stationary cutting members are generally known as "diamond bits." References herein to "diamond bits" or "diamond drill bits" refer to all types of bits generally used in the oil and gas industry, for either drilling or coring, having primarily stationary diamond cutting members.
Conventional diamond drill bits have a variety of different types of cutting surfaces, for example, polycrystalline diamond compact (PDC) cutters, thermally stable diamond product (TSP) cutters, mosaic-type cutters, natural diamonds and diamond impregnated stud cutters. Mosaic cutters are typically formed of a plurality of geometrically-shaped thermally stable diamond elements cooperatively arranged and bonded in a desired shape, to form a unitary cutting surface.
In conventional diamond bits, the diamond cutting surface is typically bonded to a supporting member which is then secured to a carrier member which facilitates attachment to the drill bit. The cutting surface is preferably connected to the supporting member by brazing or sintering. Preferably, the supporting member and the carrier member are formed of a suitable hard or sintered metal such as tungsten carbide. The supporting member can be soldered or otherwise connected, such as by form sintering or hot isostatic pressing, to the carrier member. A discussion of such a conventional structure is found in U.S. Pat. No. 4,498,549 issued Feb. 12, 1985 which is hereby incorporated herein for all purposes.
PDC diamond cutting elements can be made by forming an amalgam of polycrystalline sintered diamond and cobalt carbide which is sintered into disk shapes. Such diamond elements are commercially manufactured by the General Electric Company under the trademark STRATAPAX. These diamond elements are bonded, usually by a diamond press, to a cobalt carbide slug and sold as an integral slug cutter. The slug cutters are then attached by the drill bit manufacturers to a tungsten carbide slug which is fixed within a drill bit body according to the design of the bit manufacturer.
It has been proposed that improved drill bits can be formed by applying a layer of polycrystalline diamond by chemical vapor deposition onto a substrate of one of: (a) a metal bonded hard material compound; (b) a ceramic material; or (c) a metal or alloy. Such a concept is disclosed in U.S. Pat. No. 4,707,384 to Schachner, et al. Methods of forming diamond films and layers are disclosed in U.S. Pat. No. 4,707,384, the teachings of which are incorporated herein by reference.
Various methods have been devised for forming diamond films or coatings. One such method is disclosed in U.S. Pat. No. 4,707,384. Another method is disclosed by E. V. Spitsyn, et al., "Vapor Growth of Diamond on Diamond and Other Surfaces" J. of Crystal Growth 52, pp. 219-226 (1981). Additional methods are disclosed in U.S. Pat. Nos. 4,486,286, 4,504,519, and 4,645,977.
Continual efforts are being made to improve diamond bit technology and develop improved diamond cutting elements. It would be a significant advancement in the art to provide a diamond cutting element in which fracture resistance is greatly increased, the coefficient of friction of the cutting element surface is markedly reduced to promote separation of formation cuttings from the cutting element, and the cutting point or edge stays sharp longer than currently available elements. Such a diamond cutting element is disclosed and claimed herein.